[RFC/PATCH 5/6] revert: add --ff option to allow fast forward when cherry-picking

[Christian Couder <chriscool@tuxfamily.org>]

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
---
 builtin-revert.c |   25 +++++++++++++++++++++----
 1 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/builtin-revert.c b/builtin-revert.c
index 3cbeab7..3f92515 100644
--- a/builtin-revert.c
+++ b/builtin-revert.c
@@ -9,6 +9,7 @@
 #include "revision.h"
 #include "rerere.h"
 #include "pick.h"
+#include "reset.h"
 
 /*
  * This implements the builtins revert and cherry-pick.
@@ -31,7 +32,7 @@ static const char * const cherry_pick_usage[] = {
 	NULL
 };
 
-static int edit, no_commit, mainline, signoff;
+static int edit, no_commit, mainline, signoff, ff_ok;
 static int flags;
 static struct commit *commit;
 static int allow_rerere_auto;
@@ -51,6 +52,7 @@ static void parse_args(int argc, const char **argv)
 		OPT_BIT('x', NULL, &flags, "append commit name when cherry-picking", PICK_ADD_NOTE),
 		OPT_BOOLEAN('r', NULL, &noop, "no-op (backward compatibility)"),
 		OPT_BOOLEAN('s', "signoff", &signoff, "add Signed-off-by:"),
+		OPT_BOOLEAN(0, "ff", &ff_ok, "allow fast forward"),
 		OPT_INTEGER('m', "mainline", &mainline, "parent number"),
 		OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 		OPT_END(),
@@ -71,6 +73,8 @@ static void parse_args(int argc, const char **argv)
 	}
 	if (commit->object.type != OBJ_COMMIT)
 		die ("'%s' does not point to a commit", arg);
+	if (ff_ok && no_commit)
+		die ("options --ff and --no-commit are incompatible");
 }
 
 static char *get_encoding(const char *message)
@@ -191,7 +195,7 @@ static NORETURN void die_dirty_index(const char *me)
 	}
 }
 
-static int revert_or_cherry_pick(int argc, const char **argv)
+static int revert_or_cherry_pick(int argc, const char **argv, const char *prefix)
 {
 	const char *me;
 	struct strbuf msgbuf;
@@ -209,6 +213,19 @@ static int revert_or_cherry_pick(int argc, const char **argv)
 	if (!no_commit && index_differs_from("HEAD", 0))
 		die_dirty_index(me);
 
+	if (!(flags & PICK_REVERSE) && ff_ok && commit->parents) {
+		unsigned char head_sha1[20];
+		if (get_sha1("HEAD", head_sha1))
+			die("You do not have a valid HEAD.");
+		if (!hashcmp(commit->parents->item->object.sha1, head_sha1)) {
+			char *hex = sha1_to_hex(commit->object.sha1);
+			int res = reset(hex, prefix, HARD, 0, 0, 0, NULL);
+			if (!res)
+				fprintf(stderr, "Fast-forward to %s\n", hex);
+			return res;
+		}
+	}
+
 	if (!commit->buffer)
 		return error("Cannot get commit message for %s",
 				sha1_to_hex(commit->object.sha1));
@@ -270,11 +287,11 @@ int cmd_revert(int argc, const char **argv, const char *prefix)
 	if (isatty(0))
 		edit = 1;
 	flags = PICK_REVERSE | PICK_ADD_NOTE;
-	return revert_or_cherry_pick(argc, argv);
+	return revert_or_cherry_pick(argc, argv, prefix);
 }
 
 int cmd_cherry_pick(int argc, const char **argv, const char *prefix)
 {
 	flags = 0;
-	return revert_or_cherry_pick(argc, argv);
+	return revert_or_cherry_pick(argc, argv, prefix);
 }
-- 
1.6.6.1.557.g77031